Preheat oven to 400°F. Grease an 8-inch square baking dish.
In a large bowl, combine peaches, blackberries, lemon peel, 1/3 cup sugar and cornstarch. Distribute evenly in baking dish.
In a medium bowl, mix together flour, almonds, salt and remaining 1/2 cup brown sugar. Using a pastry blender or two knives, cut in butter until mixture resembles coarse meal. Sprinkle in an even layer over fruit.
Set baking dish onto a foil-lined baking sheet to catch any juice that might bubble over. Bake until golden and bubbling, about 30 minutes. Let cool for 10 minutes.